Combining descriptor-based analyses and mean-field modeling of the electrochemical interface to comprehend trends of catalytic processes at the solid/liquid interface

Electrocatalysis is undergoing a renaissance due to its central importance for a sustainable energy economy,relying on green(electro-)chemical processes to harvest,convert,and store energy.Theoretical considerations by electronic structure methods are key to identify potential material motifs for electrocatalytic processes at the solid/liquid interface.Most commonly,heuristic concepts in the realm of materials screening by the compilation of volcano plots are used,which rely on a plethora of simplifications and approximations of the complex electrochemical interface.While the investigation of the catalytic processes at the solid/liquid interface mainly relies on descriptor-based approaches,in the present future article it is discussed that the inclusion of the liquid part of the interface by mean-field models is crucial to elevate screening approaches to the next level.

Combined DFT and experiment:Stabilizing the electrochemical interfaces via boron Lewis acids

The incorporation of boron into carbon material can significantly enhance its capacity performances.However,the origin of the promotion effect of boron doping on electrochemical performances is still unclear,in part due to the inadequate exposure of boron configurations resulting from the complexity of traditional carbon materials.To overcome this issue,herein,a series of boron-doped graphene with highly-exposed boron configurations are prepared by tuning annealing temperature.Then the correlation between boron configurations and the electrochemical performances is investigated.The combination of density-functional theory(DFT)computation and NH3-TPD/Py-FTIR indicates that the BCO_(2)configuration formed on the surface of graphene is easier to accept lone-pair electrons than BC_(2)O and BC_(3)configurations due to the stronger Lewis acidity.Such an electronic structure can effectively reduce the number of unstable electron donors and stabilize the electrochemical interface,which is proved by NMR,and critical for improving the electrochemical performances.Further experiments confirm that the optimized BG800 with the largest amount of BCO_(2)configuration presents ultralow leak current,improved cyclic stability,and better rate performance in SBPBF4/PC.This work would provide an insight into the design of high-performance boron-doped carbon materials towards energy storage.

Effect of moderately thermophilic bacteria on metal extraction and electrochemical characteristics for zinc smelting slag in bioleaching system

The effects of moderately thermophilic bacteria on the extraction of metals from zinc smelting slag and electrochemical characteristics of zinc smelting slag carbon paste electrode in bioleaching process were studied. The results show that the extraction rates of Fe, Cu and Zn from the slag reach 86.7%, 90.3% and 66.7% after adsorbed bacteria sterilize, while those with adsorbed bacteria are 91.9%, 96.0% and 84.5% in conditions of pulp density 2%, pH 1.0, temperature 65 °C and stirring rate 120 r/min, respectively. Some stretching peaks of functional groups from bacterial secretes on the bioleached residue surface, such as 1007 cm-1 and 1193 cm-1, turn up through FI-IR analysis and indirectly reveal the presence of the adsorbed bacteria on the slag particles surface. Besides, the corrosion of zinc smelting slag is enhanced by bacteria according to the characteristics of cyclic voltametry and Tafel curves in bioleaching system.

Preparation, characterization and electrochemical properties of boron-doped diamond films on Nb substrates

A series of boron-doped polycrystalline diamond films were prepared by hot filament （HF） chemical vapor deposition on Nb substrates. The effects of B/C ratio of reaction gas on film morphology, growth rate, chemical bonding states, phase composition and electrochemical properties of each deposited sample were studied by scanning electron microscopy, Raman spectra, X-ray diffraction, microhardness indentation, and electrochemical analysis. Results show that the average grain size of diamond and the growth rate decrease with increasing the B/C ratio. The diamond films exhibit excellent adhesion under Vickers microhardness testing （9.8 N load）. The sample with 2% B/C ratio has a wider potential window and a lower background current as well as a faster redox reaction rate in H2SO4 solution and KFe（CN）6 redox system compared with other doping level electrodes.

Chemically Modified Ordered Mesoporous Carbon/Polyaniline Composites for Electrochemical Capacitors

Chemically modified ordered mesoporous carbon CMK-3 materials were prepared by means of an easy wet-oxidative method in 2 mol/L nitric acid aqueous solution. A large amount of oxygen-containing functional groups were introduced onto the CMK-3 surface. Modified CMK-3（m-CMK-3） and aniline monomer were polymerized via an in situ chemical oxidative polymerization method. Morphological characterizations of m-CMK-3/PANI （polyaniline） composites were carried out via field emission scanning electron microscopy（SEM）. Their electrochemical properties were investigated with cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The m-CMK-3/PANI composites have excellent properties in capacitance, and the highest specific capacitance（SC） value was up to 489 F/g, suggesting their potential application in the electrode material for electrochemical capacitors.

Preparation of activated carbons from mesophase pitch and their electrochemical properties

The influences of molar ratio of KOH to C and activated temperature on the pore structure and electrochemical property of porous activated carbon from mesophase pitch activated by KOH were investigated. The surface areas and the pore structures of activated carbons were analyzed by nitrogen adsorption, and the electrochemical properties of the activated carbons were studied using two-electrode capacitors in organic electrolyte. The results indicate that the maximum surface area of 3 190 m2/g is obtained at molar ratio of KOH to C of 5:1, the maximum specific capacitance of 122 F/g is attained at molar ratio of KOH to C of 4:1, and 800 ℃ is the proper temperature to obtain the maximum surface area and capacitance.

Preparation of Large-Scale Double-Side BDD Electrodes and Their Electrochemical Performances

Boron doped diamond(BDD)performs well in electrochemical oxidation for organic pollutants thanks to its wide electrochemical window and superior chemical stability.We presented a method to obtain well-adherent large-scale BDD/Nb electrode by the modified hot filament chemical vapor deposition system(HFCVD).SiC particles were sand blasted to enhance the adhesion of BDD coating.The BDD coating was then deposited on both sides of Nb which was placed vertically and closely with filament grids on both sides.The BDD/Nb electrodes had no deformation because the thermal deformations of the BDD films on both sides of the Nb substrate conteracted each other during cooling process after deposition.The surface morphology and purity of the BDD/Nb electrode were analyzed by Raman and scanning elestron microscope(SEM)techniques.Scratch test was used to investigate the adhesion of BDD films.The electrochemical performances were measured by cyclic voltammetry test.The BDD electrode at the B/C ratio of 2 000×10^(-6) held a higher oxygen evolution potential thanks to its high sp3 carbon content.Accelerated life test illustrated that the sandblasting pretreatment obviously enhanced the adhesion of BDD coating which resulted in a longer service duration than the un-sandblasted one.

Soft chemical synthesis and electrochemical properties of tin oxide-based materials as anodes for lithium ion batteries

A novel soft chemical approach was developed to synthesize tin oxide-based powders. The microstructure, morphology, and electrochemical performance of the materials were investigated by X-ray diffraction, scanning electron microscope and electrochemical methods. The results show that the particles of tin oxide-based materials form an interconnected network structure like mesoporous material. The average size of the particles is about 200 nm. The materials deliver a charge capacity of more than 570 mA·h·g-1. And the capacity loss per cycle is about 0.15% after being cycled for 30 times. The good electrochemical performance indicates that tin oxide-based materials are promising anodes for lithium ion batteries.

Electrochemically switched ion exchange performances of capillary deposited nickel hexacyanoferrate thin films

Thin films of capillary deposited nickel hexacyanoferrate(NiHCF) were investigated as electrochemically switched ion exchange(ESIX) materials. The films were generated on platinum and graphite substrates based on the ternary reagent diagram. In 1 mol/L KNO3 solution, cyclic voltammetry(CV) combined with energy-dispersive X-ray spectroscopy(EDS) was used to determine the influence of experimental conditions on the electroactivity of the NiHCF thin film on Pt substrates. The ion selectivity, ion-exchange capacity and the regenerability of NiHCF films on Pt and graphite substrates were investigated. The experiment results show that the NiHCF thin films from Ni2+-poor growth conditions have double peaks CV curves and contain relatively larger amount of potassium; while those from Ni2+-rich growth conditions are single peak CV curves and contain relatively smaller amount of potassium. It is demonstrated that the NiHCF thin films of capillary chemical deposition have good ESIX performances.

In situ characterization of natural pyrite bioleaching using electrochemical noise technique

An in situ characterization technique called electrochemical noise（ECN） was used to investigate the bioleaching of natural pyrite.ECN experiments were conducted in four active systems（sulfuric acid,ferric-ion,9k culture medium,and bioleaching solutions）.The ECN data were analyzed in both the time and frequency domains.Spectral noise impedance spectra obtained from power spectral density（PSD）plots for different systems were compared.A reaction mechanism was also proposed on the basis of the experimental data analysis.The bioleaching system exhibits the lowest noise resistance of 0.101 MΩ The bioleaching of natural pyrite is considered to be a bio-battery reaction,which distinguishes it from chemical oxidation reactions in ferric-ion and culture-medium（9k） solutions.The corrosion of pyrite becomes more severe over time after the long-term testing of bioleaching.

Electrochemical behavior and polishing properties of silicon wafer in alkaline slurry with abrasive CeO_2

The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silicon wafer with the slurry pH value and the concentration of abrasive CeO2 were studied by polarization curve technologies.The dependence of the polishing rate on the pH and the concentration of CeO2 in slurries during chemical mechanical polishing(CMP)were also studied.It is discovered that there is a large change of φcorr and Jcorr when slurry pH is altered and the Jcorr reaches the maximum(1.306 μA/cm2)at pH 10.5 when the material removal rate(MRR)comes to the fastest value.The Jcorr increases gradually from 0.994 μA/cm2 with 1% CeO2 to 1.304 μA/cm2 with 3% CeO2 and reaches a plateau with the further increase of CeO2 concentration.There is a considerable MRR in the slurry with 3% CeO2 at pH 10.5.The coherence between Jcorr and MRR elucidates that the research on the electrochemical behavior of silicon wafers in the alkaline slurry could offer theoretic guidance on silicon polishing rate and ensure to adjust optimal components of slurry.

Synthesis and electrochemical properties of SnO_2-CuO nanocomposite powders

SnO2-CuO nanocomposite powders were prepared by chemical coprecipitation method using SnCl4·5H2O, NH3·H2O and Cu(NO3)2·3H2O as raw materials. The powders were characterized by thermogravimertric(TG) analysis and differential thermal analysis(DTA), X-ray diffraction(XRD), and scanning electron microscope(SEM). The electrochemical properties of SnO2-CuO and undoped SnO2 powders as anode materials of lithium ion batteries were investigated comparatively by galvanostatic charge-discharge experiments and AC impedance. The results show that SnO2-CuO nanocomposite powders with the average particle size of 87 nm can be obtained by this method. The structure of SnO2 does not change with the introduction of CuO, but the average particle size of nano-SnO2 decreases. SnO2-CuO nanocomposite powders show a reversible capacity of 752 mA·h/g and better cycleability compared with nano-SnO2. The capacity retention rates after 60 cycles of nano-SnO2-CuO and SnO2 are 93.6% and 92.0% at the charge- discharge rate of 0.1 C, respectively, which suggests that the introduction of CuO into SnO2 can improve the cycleability of nano- SnO2.

Hierarchical Co3O4 Microstructures Decorated with Ag and Cu Oxides： Study of Photocatalytic and Electrochemical Properties

Three-dimensional hierarchical Co3O4 microstructures decorated with Ag and Cu oxides were prepared via displacement reaction and subsequent annealing treatment.Photocatalytic properties measurements revealed that the photocatalystic activities of Cu O/Co3O4 composites（Co3O4 microstructures decorated with Cu O）were enhanced while those of Ag2O/Co3O4 composites（Co3O4 microstructures decorated with Ag2O）were reduced,when compared with those of pure hierarchical Co3O4 microstructures toward the degradation of methyl orange.In addition,Cu O/Co3O4 composites exhibited an excellent recyclability ability of photodegradation.The electrochemical properties test indicated that both of the composite oxide electrodes exhibited excellent pseudocapacitive performance with relatively high specific capacitance and good long-term cycling stability.With the increase of the loaded Ag2O and Cu O dosages deposited on the Co3O4 microstructures surface,the specific capacitance values of the composites were increased.Ag2O/Co3O4 composite electrodes showed higher specific capacitance values and better cycling stability than Cu O/Co3O4 composite ones.

Electrochemical process of sulfur in carbon materials from electrode thickness to interlayer

Lots of efforts have been done on different porous carbon materials as cathode for Lithium–sulfur(Li–S)battery. However, seldom researches have been done on the relationship between cathode thickness and electrochemical performance. Our work investigates the relation between electrochemical performance and cathode thickness with typical porous carbon materials. We explain the phenomenon that only a modest cathode thickness can have the most adequate electrochemical reaction trend through the aspect of thermodynamics(chemical potential) so that the best electrochemical performance can be obtained.Besides, interlayer can remit the shuttle effect but hinder the lithium ion diffusion process simultaneously. And we verify the effect of interlayer thickness on the shuttle effect and lithium ion diffusion process.

Effects of chemical coating with Ni on electrochemical properties of Mg_2Ni hydrogen storage alloys

The effects of nickel coating on the electrochemical properties of Mg2Ni hydrogen storage alloys are presented in this paper. X-ray diffraction （XRD） and scanning electron microscope （SEM） techniques were employed to examine the crystal structure and surface morphologies of the bare and Ni-coated Mg2Ni alloys. The electrochemical properties of alloys were characterized by cyclic voltammetry （CV） and dectrochemical impedance spectroscopy （EIS）. The results showed that Ni coating not only decreased the charge transfer resistance, but also decreased the H atom diffusion resistance for Mg2Ni alloys. It was also found that Ni coating effectively improved the discharge capacity, but decreased the cycling performance of the as-synthesized Ni-coated MgzNi alloys. The discharge current has a great impact on the cycling perform- ance of the as-synthesized Ni-coated Mg2Ni alloys.

Chemical Treatment of Carbon Nanotubes as Electrodes in Electrochemical Double-Layer Capacitors

Multi-walled carbon nanombes with homogeneous diameters （40 - 60 nm）, produced by chemical vapor deposition of hydrocarbon gas, are purified by nitric acids. Infrared and Raman studies indicate that oxygen containing surface groups, which are predominately carboxylic, phenolic and lactonic groups, are introduced into purified carbon nanotubes. Then three kinds of block-form porous tablets of carbon nanotubes are fabricated as electrodes in electrochemical double-layer capacitors. Using mounded mixture comprising carbon nanotubes and binder powders provides these tablets. Comparison of the effect of different processing on the structural performance of the capacitors is specifically investigated. Using chemically treated electrodes, electrochemical double-layer capacitors with a specific capacitance of about 33 F/g are obtained with 38 wt % H2SO4 as the electrolyte.

Synthesis and Temperature-dependent Electrochemical Properties of Boron-doped Diamond Electrodes on Titanium

On the sand-blasting-treated titanium（Ti） substrate, the boron-doped diamond（BDD） electrodes with a wide potential window were prepared by microwave plasma chemical vapor deposition（MPCVD）. The electrochemi- cal oxidation ratios of phenol at BDD/Ti electrodes at elevated temperatures（from 20 ℃ to 80 ℃） were examined by the chemical oxygen demand（COD） of phenol electrolyte during electrolysis. The results show that the COD removal was increased at high temperatures and the optimized temperature for enhancing the electrochemical oxidation ratio of phenol is 60 ℃. The mechanism for the temperature-dependent electrochemical oxidation ratios of phenol at the electrodes was investigated. The study would be favorable for further improving the performance of BDD/Ti elec- trodes, especially working at high temperatures.

Controlled Growth of Well-Aligned Carbon Nanotubes, Electrochemical Modification and Electrodeposition of Multiple Shapes of Gold Nanostructures

An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapour deposition (CVD). Free-standing MWCNTs arrays were functionalized through electrochemical oxidation with the formation of hydroxyl and carboxyl functional groups. Using a new oven drying technique, we demonstrate that the unidirectionally aligned and laterally spaced geometry of the CNT arrays can be retained after being subjected to each step of electrochemical modification. Samples were analyzed by using a field emission scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transformed infrared (FTIR) and Raman spectroscopy. Useful electrochemical methods for the synthesis of various gold nanostructures onto the aligned MWCNTs were then presented for the first time. The results demonstrated that flowerlike nanoparticle arrays, nanosheets and nanoflowers were obtained on the aligned CNTs under different experimental conditions. These kinds of aligned-CNT/Au nanostructures hybrid materials introduced by these efficient and simple electrochemical methods could lead to development of a new generation device for ultrasensitive catalytic and biological application.

DEVELOPMENT OF A PRECISE ELECTRO CHEMICAL INTERFACE

Based on the circuit principle of 1186 Electro Chemical Interface preduced by Solartron Electronic Group Ltd., a precise electro chemical interface (ECI) unit, which can provide the interfacing requirements for the control and measurement of characteristics of electro chemical cell, was developed by means of some essential improvements. Not only can it be used to control and measure the steady and non-steady state characteristics, but also it can be directly connected with Solartron 1170 series or 1250 Frequency Response Analysers (FRA) to measure the AC impedance. Besides,the EC1 can also be connected with two- or three-electrode electro chemical cell systems to test convenlently and correctly their DC and AC characteristics, and used as a four-electrode potentlostat combined with four-electrode electro chernical cell system which contains two reference electrodes (RES) for researches on the electro chemical characteristics of oil-water interface, etc.

Unraveling the decomposition mechanism of Li_(2)CO_(3)in the aprotic medium by isotope-labeled differential electrochemical mass spectrometry

Rechargeable lithium-ion batteries(LIBs)represent the highest energy density in the contemporary energy storage community,typically delivering a practical energy density of 150-350 Wh kg-1in the current technique,which can hardly satisfy the evergrowing demand for the portable electronic devices and power tools requiring long service time[1-3].